Inkjet CTP technique is a technique that utilizes an inkjet printing apparatus to spray images directly on a metal substrate or a polymer substrate. The metal substrate for plate making may be a zinc plate, copper plate, or aluminum plate. To improve the durability and resolution of the metal substrate, usually the metal substrate is roughened (see CN85100875) to a certain degree of roughness on its surface. At present, the roughening methods may be categorized into methods that utilize anodization and methods that don't utilize anodization. The anodization process is matured and widely applied. Usually, the roughness parameter Ra of the metal substrate surface after anodization treatment is Ra=0.6˜0.9 μm (Ra is a height parameter, i.e., the arithmetic mean deviation of profile). However, to avoid severe environmental pollution that may be caused by a large quantity of acid or alkali waste liquid and increased overall manufacturing cost of the finished plate, a method that doesn't utilize anodization may be used to treat the metal substrate.
The main object of the present invention is to prepare a metal substrate that has appropriate roughness as well as high absorbency and wearability and can be used for Inkjet CTP, by roughening the metal substrate by anodization or through a method that doesn't utilizes anodization and then applying hydrophilic polymer paint on the surface of the metal substrate, or directly applying hydrophilic polymer paint on the surface of the metal substrate. In the present invention, the raw material of the metal substrate paint is cheap, and the method for preparing the metal substrate is simple.